[PATCH 12/13] locking/qspinlock: separate pv_wait_node from the non-paravirt path

From: Nicholas Piggin
Date: Mon Jul 04 2022 - 10:40:00 EST


pv_wait_node waits until node->locked is non-zero, no need for the
pv case to wait again by also executing the !pv code path.

Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
kernel/locking/qspinlock.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 9db168753124..19e2f286be0a 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -862,10 +862,11 @@ static inline void queued_spin_lock_mcs_queue(struct qspinlock *lock, bool parav
/* Link @node into the waitqueue. */
WRITE_ONCE(prev->next, node);

+ /* Wait for mcs node lock to be released */
if (paravirt)
pv_wait_node(node, prev);
- /* Wait for mcs node lock to be released */
- smp_cond_load_acquire(&node->locked, VAL);
+ else
+ smp_cond_load_acquire(&node->locked, VAL);

/*
* While waiting for the MCS lock, the next pointer may have
--
2.35.1